U.S. Pat. Nos. 3,429,796 and 6,176,989 disclose sensors that are replaceable units widely used with gas-analyzing instruments for measuring the amount of a specific gaseous constituent of a gas stream, for example oxygen in a methane gas stream. The operation of such sensors is based on an oxidation-reduction reaction occurring that causes an electrical current to flow between a cathode and anode within the sensor. The sensor is mounted to, or otherwise connected, in a fashion where a sample portion of gas from the gas stream flows into the sensor. The useful life of these sensors varies depending on the chemical composition of the gas being analyzed, the volume of sampled gas flowing into the sensor, the chemical composition of the cathode and anode of the sensor, and other factors. In the manufacture of these sensors defects frequently occur that create quality assurance problems.